In accordance with the miniaturization and high performance designing of a variety of electronic devices including personal computers, digital cameras, cell phones and the like, there is rapidly increasing a demand for further miniaturization, thinning and high densification of semiconductor devices. Hence, in high-density mounting technologies that are able to cope with an increasing substrate area in productivity growth and cover chip-size packages or chip-scale packages (CSP) or three-dimensional laminates, there have been demanded developments of photosensitive insulating materials of the type adapted for application to structures that have fine irregularities of high aspect ratio on a substrate.
For such a photosensitive insulating material as set out above, there has been proposed a photocurable resin composition (Patent Document 1: JP-A 2008-184571), which is applicable over a wide range of film thickness according to a spin coating technique ordinarily employed in a semiconductor device manufacturing procedure, is able to form a micropattern within a wide wavelength region and is able to provide a film for protecting electric and electronic parts by low-temperature after-curing as having excellent flexibility, heat resistance, electric characteristics, adhesion, reliability and chemical resistance. However, if this photocurable resin composition is coated onto a substrate having surface irregularities by the spin coating technique, a difficulty is involved in coating the substrate therewith substantially in a uniform way. More particularly, the photocurable resin composition is apt to establish spaces at stepped portions on the substrate and thus, further improvements in flatness and step coverage have been expected. For other coating techniques used in place of the spin coating technique, a spray method has been proposed (Patent Document 2: JP-A 2009-200315). However, such a method is liable to cause, in principle, defects such as a difference in height owing to the irregularities of the substrate, or no film formation at a pattern edge and pinholes at a bottom recess. Hence, the problems on the flatness and step coverage have not been solved satisfactorily yet.